Lightsabers are not only one of the coolest looking weapons in all of science fiction, but they're also the elegant weapons of the Jedi Knights, the guardians of peace and justice in the galaxy, as well as of the Sith, the ancient order pledged to destroy them. Every Jedi and Sith must construct their own lightsaber in order to successfully complete their training in the Light Side or the Dark Side.
Lightsabers derive their blade color from the Kyber crystals located inside them. Jedi must seek out these crystals and forge a bond, from which their traits will influence the natural clear state of the crystal. Sith by contrast either synthetically create their own cause the crystals to "bleed." Lightsaber colors can denote everything from a Jedi's connection to the Living Force to whether or not they're most suited to be a fighter or an ambassador. You won't need to seek out a Jedi Holocron to learn about the different colors; below is every major lightsaber color and what it means.
Blue lightsabers are by far one of the most prolific lightsaber colors in the Jedi Order. In the Star Wars films and animated television series, the most famous Force users to wield blue lightsabers are Anakin Skywalker, his son Luke Skywalker, his Jedi Master, Obi-Wan Kenobi, and Ezra Bridger of Star Wars: Rebels.
Blue lightsabers are typically wielded by Jedi Guardians or those that seek to defend the Order from outside malevolence that would do it harm. These Jedi are the most highly trained in the Jedi combat arts and are the Order's most adept and accomplished duelists.
Green lightsabers were typically used by Jedi that had a strong connection to The Force (specifically with the Living Force) and Jedi Consulars, one of the three paths a Jedi could follow after their ascension to Jedi Knight. The Living Force was a view held by Jedi that were mindful of the living beings around them and the energy they created and drew heightened perspective from it.
Qui-Gon Jinn and Master Yoda were some of the most famous examples of Force users that wielded green lightsabers and heeded the Living Force. Not only did it often make them useful ambassadors (like most Jedi Consulars), it was through this process that they were able to conserve their identities after the death of their corporeal form and become one with The Force.
Red lightsabers were never used by Jedi Knights due to the nature of their forging. Since Kyber crystals are living entities whose colors alter with the connection created by a Force user, they are capable of experiencing pain. The red color is therefore created by Dark Side users causing the crystals to "bleed" from their suffering.
The Sith utilized red lightsabers almost exclusively. After Darth Bane implemented the Rule of Two, it was also an easy way to identify their kind. Famous wielders of red lightsabers include Darth Sidious, Darth Vader, Darth Maul, and Lord Tyranus. Kylo Ren, a Dark Side warrior who isn't Sith, still wields a red blade after forsaking the Jedi Path.
One of the most unique lightsaber colors in the Star Wars Saga, the purple lightsaber is a distinct blade color that isn't seen in great numeration. According to Claudia Gray's novel Master and Apprentice, the color is a manifestation of the properties of the Jedi bonding to its Kyber crystal.
The most famous wielder of a purple lightsaber was Jedi Master Mace Windu, who was one of the only Jedi strong enough to practice Form VII, a style of lightsaber combat that required a Jedi to be dangerously close to the Dark Side. The purple lightsaber blade can, therefore, be seen as a careful temperament between the Light and Dark Side from its wielder.
Yellow lightsabers are some of the rarest blades to be wielded by a member of the Jedi Order. Jedi Master Plo Koon and Ahsoka Tano have been known to utilize them on occasion, but they are primarily the blade color of the Jedi Sentinel. The Jedi Sentinels comprised one of the three paths afforded to a padawan after they became a Jedi Knight.
Sentinels understood not every problem could be solved by the Force and often utilized a great deal of practical knowledge that made them expert spies. The yellow color reflects a balance between the green of the Jedi Consular and the blue of the Jedi Guardian. Sentinels were exclusively employed as Jedi Temple Guards.
White lightsabers are almost exclusively associated with one character: Ahsoka Tano. Once the apprentice of Anakin Skywalker, she left the Jedi Order on poor terms, and, as a result, had to relinquish the use of her twin green lightsabers. It was on the farming moon Raada, after an encounter with a Sixth Brother of the Inquisitorius, that she created the white lightsabers.
Since his twin lightsabers were red, the color of a Dark Side user, she had to restore the Kyber crystals to their original clear state. They remained in this form while she aided the crew of The Ghost in Star Wars: Rebels, and was able to face her former Master with her twin white sabers.
The black lightsaber, or the Darksaber, is the only one of its kind known to exist. It was created by the first Mandalorian ever to be inducted in the Jedi Order, Tarre Vizla. It features a unique black plasma blade, flat and curved like a traditional "saber" blade rather than a beam of energy, and has the ability to "draw" other lightsaber blades to it, making attacks to the wielder almost impossible.
The Darksaber allowed Vizla to become the Mand'alor, or ultimate ruler of his homeworld. After his death, the Darksaber became the property of the Jedi Temple until members of House Vizla came looking for it. It is said only when the wielder is bested in combat may the Darksaber be relinquished.